ЕБАНЫЙ РОТ ЭТОГО КАЗИНО БЛЯТЬ

#ifdef _DEBUG
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

#define X first
#define Y second
#define inb push_back
#define mk make_pair
#define all(v) (v).begin(), (v).end()
#define sqr(x) ((x) * (x))

int solve()
{
    int n, m;
    double s;
    cin >> n >> m >> s;
    vector<pair<int, double>> p(m);
    for (int i = 0; i < m; ++i)
    {
        int pt;
        double tt;
        cin >> tt >> pt;
        p[i] = mk(pt, tt / s);
    }
    vector<double> dp(n);
    for (int it = 0; it < 100000; ++it)
    {
        for (int c = 0; c < n; ++c)
        {
            dp[c] = 0;
            for (int i = 0; i < m; ++i)
            {
                double cur = 0;
                if (c + p[i].X > n - 1)
                {
                    cur += p[i].Y;
                }
                else
                {
                    cur += dp[c + p[i].X] * p[i].Y;
                }
                if (c)
                {
                    cur += dp[c - 1] * (1.0 - p[i].Y);
                }
                dp[c] = max(cur, dp[c]);
            }
        }
    }
    cout << setprecision(15) << fixed << dp[n - 1];
    return 0;
}

int main()
{
    #define TASK "casino"
    #ifdef _DEBUG
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
    #else
    freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
    #endif
    solve();
    return 0;
}